[rescue] Trying to get Cadmus 9200 running (serial console trouble)

[Dave McGuire]

On 2/6/19 3:16 AM, Meelis Roos wrote:
>>> I retried it. it's less consistent than I remembered.
>>>
>>> Aaa at a@aa at aa@aaaaaaAaA at AAaAa@aAcssssbscsbbsbbsbssbd``DD at d@`@d`d at d@ddD at D@`@`dDDDddfDfDDfDdDfffDf
>>>
>>>
>>> ``qqqqqqqqqaaq`qqqqa`a`aqqqqq`qaq`qvwwwwwvwwwwwgwvwwwvwwwwwADeDe at eAe@eDDaDdaeEeaeaDae`eDED
>>
>> B B  Hmmm.B  Is it possible that it's a differential serial line, like RS423
>> or similar?B  If that's the case, if the other line of the differential
>> pair isn't grounded, I've seen exactly this sort of behavior.
> 
> Docs say it's standard RS-232. There is an option card for 20mA current
> loop that has + and -
> for both Rx ja Rx but that is clearly with a separate conversion adapter
> only.

  Hrm.  Ok.  But that pattern looks awfully familiar.  Maybe a ground
discontinuity?

> Perhaps I just got some not connected pin to PC side Rx and the cable
> picked up some noise?
> But that seems unlikely as RS-232 should not pick up anything below +-3V
> and "antenna" should
> not induce volatages over 3V here, I think.

  That can easily happen, actually, depending on the input impedance of
those line receivers.

           -Dave

-- 
Dave McGuire, AK4HZ
New Kensington, PA